This application claims the benefit of Korean Patent Application No. 2002-53160, filed on Sep. 4, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference
1. Field of the Invention
The present invention relates to a single-panel color image display apparatus, and more particularly, to a colored light separating device having high optical efficiency due to color scrolling and a single-panel color image display apparatus using the same.
2. Description of the Related Art
Projection type color image display apparatuses form an image by controlling the on/off operation of light emitted from a high-power lamp light source on a pixel-by-pixel basis using a micro display (which is also called a light valve) such as a liquid crystal display (LCD) or a digital micro display (DMD), magnify and project the image using a projection optical system, and provide a wide picture. Projection type color image display apparatuses are classified into a three-panel projection type and a single-panel projection type, depending on the number of micro displays.
In a general single-panel color image display apparatus, white light irradiated from a white light source is separated into red, green, and blue using a color wheel, and the three colors are sequentially sent to one micro display. The micro display operates according to the sequence of colors received, and forms an image.
The general single-panel color image display apparatus has a simpler structure and a smaller optical system than a three-panel color image display apparatus, which forms images for each color on three micro displays using an optical separation/combination system, but provides an optical efficiency of ⅓ less than that of the three-panel color image display apparatus due to the use of the color wheel. To solve the reduction problem of the optical efficiency in the general single-panel color image display apparatus using the color wheel, a single-panel color image display apparatus using a color scrolling technique has been proposed as shown in FIG. 1.
In the color scrolling technique, white light is separated into a red colored light R, a green colored light G, and a blue colored light B, and the three colors are sent to different locations on a micro display, thus forming R, G, and B color bars. Further, the color bars are moved at a constant speed in a particular method so that an image may be formed after the R, G, and B colors for each pixel reach the micro display.
Referring to FIG. 1, in a conventional single-panel image display apparatus, white light emitted from a lamp light source 30 passes through first and second lens arrays 32 and 34 and a polarizing beam splitter array 35 and is condensed by a condensing lens 37. The white light is separated into R, G, and B colors by first through fourth dichroic filters 39, 42, 69, and 52, and the R, G, and B colors are combined.
To be more specific, the red colored light R and the green colored light G are transmitted by the first dichroic filter 39 and travel along a first optical path l1, while the blue colored light B is reflected by the first dichroic filter 39 and travels along a second optical path l2. The red colored light R and the green colored light G on the first light path l1 are separated by the second dichroic filter 42. The red colored light R is transmitted by the second dichroic filter 42 and travels along the first light path l1. The green colored light G is reflected by the second dichroic filter 42 and travels along the third light path l3.
The green colored light G and the blue colored light B that travel along the second and third optical paths l2 and l3, respectively, are transmitted and reflected, respectively, by the third dichroic filter 69, and are thus combined. Finally, the R, G, and B light beams are combined by the fourth dichroic filter 52. The combined light passes through a polarizing beam splitter 57 and is incident on a micro display 60.
First through third prisms 44, 65, and 72 are disposed on the first through third optical paths l1, l2, and l3, respectively, and rotate at a uniform speed such that R, G, and B color bars are formed on the micro display 60, and are scrolled due to the rotation of the first through third prisms 44, 65, and 72.
As described above, in the conventional single-panel image display apparatus, while the white light emitted from the light source 30 is separated and combined by the first through fourth dichroic filters 39, 42, 69, and 52, color scrolling is performed as the first through third prisms 44, 65, and 72 disposed on the first through third optical paths l1, l2, and l3 rotate.
The scrolling of the R, G, and B color bars due to the rotation of the first through third prisms 44, 65, and 72 is shown in FIG. 2. FIG. 2 shows the movement of the R, G, and B color bars formed on a surface of the micro display 60 when the prisms 44, 65, and 72 corresponding to the R, G, and B colors are synchronously rotated.
The micro display 60 processes image information for each pixel to synchronize with the movement of the R, G, and B color bars and forms an image. The formed image is magnified by a projecting lens (not shown) and projected on a screen (not shown).
As described above, the conventional single-panel image display apparatus has the structure in which light is separated into individual colors and the separated colors are combined. Relay lenses 41, 47, 50, 54, 61, 67, 70, and 75, which are disposed on optical paths between optical components, send light to the polarizing beam splitter 57. Accordingly, optical paths are complicated, and multiple components are disposed on the complicated optical paths so that the conventional single-panel image display apparatus has a large optical system, and an assembling process of the multiple components is difficult.
Further, since color scrolling is performed due to the individual rotation of the three prisms 44, 65, and 72, it is difficult to synchronize the driving of the micro display 60 with the three prisms 44, 65, and 72.
That is, the color bars as shown in FIG. 2 must be moved at a constant speed to form a color image using the color scrolling technique. However, since the conventional single-panel image display apparatus must synchronize the micro display 60 with the three prisms 44, 65, and 72 to perform scrolling, controlling the synchronization is difficult. Further, since the three prisms 44, 65, and 72 move in a circular motion, the color scrolling speed is not constant, thus impairing the quality of an image.
In addition, a large amount of noise is generated due to the driving of three motors to rotate the three prisms 44, 65, and 72, and the manufacturing costs of the conventional single-panel image display apparatus using three motors is higher compared to a color wheel method using only one motor.
The present invention provides a colored light separating device having a simple structure for color scrolling and a single-panel color image display apparatus using the same.
According to an aspect of the present invention, a single-panel color image display apparatus includes a light source; a colored light separating device, which comprises a colored light separator having a plurality of dichroic filters to separate light emitted from the light source into a plurality of colored light beams and a driving device to drive the colored light separator to scroll the separated colored light beams; and a micro display, which controls light, which is separated by the colored light separator according to color and scrolled according to the driving of the colored light separator, on a pixel-by-pixel basis according to an input image signal and forms a color image.
The driving device may enable the colored light separator to move straight, pivot, or rotate.
The plurality of dichroic filters may be of a reflective type.
The plurality of dichroic filters may be parallel to one another.
The single-panel color image display apparatus may further include a first lens array which is disposed between the light source and the colored light separator and converts light incident from the light source into condensing light.
The single-panel color image display apparatus may further include second and third lens arrays which are disposed between the colored light separator and the micro display.
The single-panel color image display apparatus may further include a relay lens which is disposed between the third lens array and the micro display.
A distance among the plurality of dichroic filters of the colored light separator may be set such that colored light beams separated by the colored light separator are incident on the same lens cell of the second lens array without color mixture.
A minimum distance by which the colored light separator may be moved along a straight line may be set such that the colored light may be moved from one lens cell to another lens cell of the second lens array.
A minimum angle by which the colored light separator may be pivoted may be set such that the colored light may be moved from one lens cell to another lens cell of the second lens array.
According to another aspect of the present invention, a colored light separating device may perform colored light separation and color scrolling, the device including: a colored light separator which includes a plurality of dichroic filters to separate incident light into a plurality of colored light beams; and a driving device which moves the colored light separator to scroll the separated colored light beams.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.